Low voltage discharge tube



Aug. 7, 1934. A. LEDERER LOW VOLTAGE DISCHARGE TUBE Original Filed Pep. 14 1929 ATTORNEYS Patented Aug. 7-, 1934 UNITED STATES PATENT OFFICE.

LOW VOLTAGE DISCHARGE TUBE Anton Lederer, Vienna, Austria;

Catherine Application February 14, 1929, Serial No. 340,027.

Renewed December 1, 1933.

ary 24, 1928 Claims.

This invention relates to vacuum tube lighting systems, such for example as that comprising the well known positive column or gaseous conductor tube lights in which the passage of a current,

5 between spaced electrodes and through a column of more or less rarified gas, such as one of the monotomic gases, as neon, causes the tube contents to glow and radiate light. Attempts have heretofore been made to produce discharge or 10' gaseous conductor tubes provided with a rare gas filling that can be operated on the lowest possible voltage and it is known that the discharge potential can be considerably reduced by the use of alkali metals, such as potassium, as electrodes, or

' by introducing into the tube an alkali metal in the form of a vapor, which will, alternately, deposit in the region of the electrodes and evaporate again during the operation of the tube. Up to the present time it has not been possible to produce tubes which can be operated on the ordinary line voltages, that is to say, on voltages as low as 110 volts.

The present invention has for its object the production of a discharge tube of this character which can be operated on voltages of 110 volts or less. In accordance with the invention, alkali metal (or mixtures thereof) is introduced into the tube in the form of a vapor together with the rare gas, such as helium, neon or other gases of the same group or mixtures thereof. Prior to the introduction of these gases and vapors the tube is evacuated to a high degree and heated to a high temperature preferably not less than 400 C. at the time that high vacuum is reached.

The alkali metal vapor should be introduced into the tube in such amounts that, during operation of the tube, particularly, the pressure of the rare gas in the tube exceeds that of the alkali metal vapor. When the alkali introduced in the tube is potassium, good results can-be obtained when the proportion of the rare gas to that of the metal vapor is 5 to from 0.04 to 4 (5:0.04 to 4).

If, therefore, the tube is filled with (say) neon, gas

at a pressure of 5 mm. of mercury, the pressure of the introduced alkali metal vapor should not exceed 4 mm.

' The discharge tube thus filled with a rare gas and alkali metal vapor can be operated with a 5m voltage of 110 or less.

In order to obtain the required reliability and stability in operation of a discharge tube of this character, it is an advantage if the surfaces of the electrodes bear a proper relation to each other,

; although it does not appear important whether In Austria Febru- (Cl. B -122) the electrodes are composed of metallic or metalloidal material.

In the preferred embodiment of this invention, it is desirable that the surface area of the cathode be greatly in excess of the surface area of the anode. For instance the relation of the surface of the anode to that of the cathode is conveniently at most 1:5 but it may also be decreased to 1:50 or less. That is to say the surface area of the cathode should be at least five times the surface area of the anode or a multiple thereof. However its surface area may also be a 50 or or still larger multiple of that of the anode. The surface area of the anode is preferably 3 square centimeters or more.

In the accompanying drawing, which is intended to illustrate one form of a lamp embodying the present invention,

Figure 1 shows an elevation of a lamp with portions broken away to more clearly illustrate the structure and Figure 2 is a transverse view of the cathode on the line 22 of Figure 1.

The positive column, between the electrodes, may be bent into various shapes and is shown as straight merely for the sakeof simplicity.

The envelope 1 contains a rare gas, e. g., neon and an alkali metal e. g. potassium. Low voltage discharge potential is applied to anode 2 and cathode 3 from generator 4' through resistance '5. The structure of the cathode is such that its surface area exceeds that of the anode as described above. To this end, the cathode may as shown, be formed of a sheet of'metal rolled into a spiral which is joined to a supporting post 6 which post is sealed into the envelope through the press 7. The post 6 is connected to lead-wire 8 which leads to the generator 4. By the means shown, and by other means, the area of the oathode can be made to be any desired multiple of that of the anode.

Various methods of manufacturing the tube and introducing the gas and vapor filling therein will occur to those skilled in the art and no limitation is intended by the phraseology of the foregoing specification, except as indicated in the appended claims.

What I claim is:-

1. An electric gas discharge illuminating lamp comprising an envelope having therein a rare gas at low pressure, an anode electrode, a cathode electrode spaced from said anode electrode so as to permit a visible positive column illumination when said electrodes are connected to a source of electric current, and so much alkali metal that the lamp will operate with a ratio of the pressures of the-gas and vapor, respectively, of 5.0 to DAM-4.0.

2. An electric gas discharge illuminating lamp comprising an envelope having therein a rare gas at approximately 5 mm. pressure, an anode electrode, a cathode electrode spaced from said anode electrode so as to permit a visible positive column illumination when said electrodes are connected to a source or electric current, and so much alkali metal that the lamp will operate with a ratio of the pressures of the gas and vapor, respectively, of 5.0 to 0.044.0.

3. An electric gas discharge illuminating lamp comprising an envelope having therein a rare gas at low pressure, an anode electrode, a cathode electrode which has a surface area at least five times the surface area of said anode eleo trode and which is spaced from said anode electrode so as to permit a visible positive column illumination when said electrodes are connected to a source of electric current, and so much alkali metal that the lamp will operate with a ratio of the pressures of the gas and vapor, respectively, or 5.0 to 0.04-4.0.

4. An electric gas discharge illuminating lamp comprising an envelope having therein a rare gas at approximately 5 millimeters pressure, an anode electrode, a cathode electrode which has a surface area at least five times the surface area of said anode electrode and which is spaced from said anode electrode so as to permit a visible positive column illumination when said electrodes are connected to a source of electric current, and so much alkali metal that the lamp will operate with a ratio of the pressures of the gas and vapor, respectively, of 5.0 to 0.044.0.

5. An electric gas discharge illuminating lamp comprising an envelope having therein a rare gas at approximately 5 millimeters pressure, an anode electrode, a cathode electrode which has a surface area of from five to fifty times the surface area of said anode electrode and which is spaced fromsaid anode electrode so as to permit a visible positive column illumination when said electrodes are connected to a source of electric current, and so much alkali metal that the lamp will operate with a ratio of the pressures of the gas and vapor, respectively, of 5.0 to 0.04-4.0.

ANTON LEDERER. 

